New batteries

[wes4dbt]

Thanks for the information.

So this 50C would work?
https://www.aliexpress.us/item/32568030 ... pt=glo2usa

Out of curiosity, would a pair of U1 35ah batteries work in my M3? I mean, 24v is 24v. I know there wouldn't be much distance available from them but that not really an issue.

[wes4dbt]

Is this the type of charger your talking about. Is that a plug match with the battery?

https://www.amazon.com/ISDT-Touchscreen ... 227&sr=8-5

[Burgerman]

The 35Ah batteries would work. Might be very gutless though as they will show a fair bit of voltage drop as you move.

The lithium batts might work, but I dont trust aliexpress 50C batteries to actually be 50C batts...

If they really are, then yes!

The charger will work.

[Burgerman]

Half sized lead batteries will give double the voltage drop that we see here.
https://www.wheelchairdriver.com/board/ ... =2&t=12575

These were a set of odyssey 68Ah ones.
Remember that when the voltage hits the lower limit it doesent drop more, instead the power mdule reduces the motor current to stop the voltage collapsing at the battery.

So while hese small lead batteries might work enough for your purposes they wouldnt for me! My programming allows very sharp acceleration, that maximises the power modules and battery capability. Most peoples doesent. So this all depends on you. How its programmed and how hard you use it. I drive everything like I stole it though.

The high C rate LiPo bateries (if they are decent quality) dont show much voltage drop at all compared even to big lead batteries.
And low C rate but large lithium cells like the 230Ah ones that STILL ARE NT HERE are the same. They will not drop voltage much at all.

[shirley_hkg]

I set to 27.4V and top up a few chairs for 24 hours that are sat unused in the house every 2 weeks too. As well as a string of old batteries in parallel at 13.7V.
...

I've been doing it a 65% DOD cycles every 2--3 months.

Every 2 weeks will be a bit too frequent for me.

I want to maintain the 85Ah gel pair, that went to UK with me last year.
Any suggested values for, say monthly or bi-monthly
EFFECTIVE top up charge ?

Here is 20 --- 34℃ around.

Thanks.

[Burgerman]

If you have them fitted in a chair then every 2 weeks...
Even if unused. Because the chairs have a small drain regardless even when off. It may be tiny, but if a lead battery is 1% discharged for a few weeks or more then that is a permanant 1% of sulfation and capacity after a while. To keep sulfation levels to as low as possible, ie almost no capacity losses, you have to maintain them as close to 101% charged as possible. Without damage from overcharge.

To do that ideally you would need a continual float voltage a fraction above the 100% charged voltage. 24/7 ontinually. Which isnt very practical for many. That is battery dependent to a degree. But is usually around 13.3 to 13.4V.

In order to get as close to that while charging intermittently without overcharge, you need to use the float charge voltage of say 13.6V to 13.7V overnight every couple of weeks in a chair.

THREE WAYS to charge.
So in use which is a cyclic charge (if discharged through use) voltage should be around 14.1V gel, 14.6V AGM for around 8 hours max, stop at 500th to 1000thC current (+ any chair draw of around 6 to 12mA depending on control system.) Or on some batteries like MK gel, charge at this voltage until current fails to drop by 0.1A per hour. At this point its FULL. This allows a 99 to 99.9% full charge in the limited overnight period we have while limiting gas or grid corrosion.

In FLOAT charging, used to charge intermittently to keep topped up, say solar use, or in an unused chair every 2 weeks, 13.6 to 13.7V is correct for most batteries. Overnight if the battery is topped off every 2 weeks and unused otherwise. This is too high for long term storage. OK for a couple of days to ensure a 101% full safe battery charge..

In a storage, maintainance long term float situations, like if the battery is in storage for more than a few weeks in a chair (or say new sat on a shelf for an unknown time in a warehouse) then use a voltage that is a fraction higher than its natural fully charged voltage. Normally this is around 13.3 to 13.35V. t can also charge a battery. But voltage not really high enough in cyclic use and a full charge may not balance cells adeqyately, and will take 2 to 3 days for a full charge. Batetries will have a short cycle life this way. A voltage this low is only for continual long term storage.

Use a little less in high summer. And a little more in cold winter. See correction factors.

If the battery is NOT FITTED in a chair, then a battery with very low self discharge like Odyssey or MK gel, can be fully charged, and ignored for a month or even two months. As it will stay at 100% (or close too it) for longer. But in a chair, top off every 2 weeks! UNLESS you can disconnect the battery with a breaker of remove a connector or something.

[shirley_hkg]

They are not in a chair.

[Burgerman]

MK temp compensation...
Same with most gels.

MK DATA:

This is CYCLIC (as in discharged in use) charge max volts, and FLOAT CHARGING as is solar or intermittent slow safe charge voltage. These are not storage float long term votages!

What does temperature do to your battery?

temp versus battery life... Warmer = very bad news!!!

Result of a few tenths of a volt too high charge voltage - MK DATA

Dont be this guy!

-A 3 STAGE CHARGE is approx 4 to 5 hours at CV and then stop, and let the lower float voltage complete the charge over 16 to 20 hours.
-A 2 STAGE charge where the CV/ABSORPTION stage continues until 8 hours has elapsed, or current falls to 1/500th to 1000th of C gives a much faster and more complete overnight charge. And no FLOAT stage required.
-A 1 STAGE (a top up for an already full but stored chair, every 2 weeks or solar charger etc) is JUST the 3rd stage, a 13.6/13.7V constant indefinite voltage overnight to a day. You can also use this in cyclic use but it takes over 24 hours to ensure a full charge.
-A LONG TERM STORAGE voltage or float is connected indefinitely at 13.3 to 13.4V in storage to keep as healthy as possible.

In CYCLIC use an 8 hour CV/ABSORPTION at 14.1V (gel) gives full rapid overnight charge. OR a shorter CV/ABSORPTION, and a 3rd stage FLOAT, gives the same result but takes longer... Around 16 to 20 hours.
If its already full, ONLY the float stage is needed to top off a battery. So 8 hours to a day at 13.6V.

[Burgerman]

All that said, anything will charge lead batteries, As most mobility chargers do. They just do it badly!

[wes4dbt]

So while hese small lead batteries might work enough for your purposes they wouldnt for me! My programming allows very sharp acceleration, that maximises the power modules and battery capability. Most peoples doesent. So this all depends on you. How its programmed and how hard you use it. I drive everything like I stole it though.

Yeah, I put very little stress on the chair. I use a low speed, the M3 is a real tank compared to the lightweight Jazzy Air 2 that I drive on a daily basis. Also I'm not very familiar with the joystick because I use the chair so infrequently. I don't want to damage anything in the dentist office, not a lot of room there. Think the speed setting is only on 2.

So the only power I'd need for the entire trip would be less than 200 yards at a slow and the power used to recline/unrecline the chair.

Hell, I might be able to do that using D size batteries. lol

[Burgerman]

Well 25v worth of those can be 10Ah if you get the right cells. But you would need about 19 of them. And they cant make the required current.

[shirley_hkg]

Put it in indefinite float is best, but electricity bill will cost more than the lead bricks. We don't have solar.

I top up this pair overnight, which has sat for 3 months.

Would like to know, if it is advisable to maintain it monthly for overnight or 24 hrs.

Voltage
Current
Duration

[Burgerman]

ZXD is overkill for this job. $$$ electricity. Will work, but not needed!

If battery is "already 99% full" - sat a month or even if it IS full... Then at 13.8V overnight is enough.

13.6V OK for 1 to 2 days. Not critical. Until current stops falling if checked over 4 hours or more.
This is actually better as overcharge is nearly impossible but its slower. At this voltage its safe to leave on for longer if in doubt. Up to a week max if in doubt or old battery?

13.5V all week to a month or so..

13.3 to 13.4V indefinitely. At this voltage current is so low ONCE FULLY CHARGED (after a long time connected), that it isnt really easy to measure. So safe indefinitely.

The AIM on a long term storage float is to hold it a tiny fraction above its fully charged voltage, so zero sulfation can happen, while almost no current flows. Because that would cause grid corrosion and electrolyte loss long term. You can fine tune this voltage long term. It is temperature dependent if it gets hot or cold enough to matter.


*********
For long term float I just use a tiny low power wall wart. Set to 26.6 to 26.7V. Takes around 1W or less.

Similar to this, but even less power.
https://www.ebay.co.uk/itm/405108313343

This is 2A
(Mine is even smaller, 1A, and has no display. On my van all winter.)

2A
3 to 36V
AC 100 to 240V input. Uses very little power. 1W?
Fit XLR.
Check accuracy with decent multimeter as these may be slightly wrong at least initially!

These can do 1 to 4 chairs at once at 24V or a stack of 12V batteries. Or even a lithium cell/pack in low-power cheap silence.